Walking through Bab al-Yemen, the main entrance to the walled city of old Sanaa, I counted more than 300 posters and placards of President Ali Abdullah Saleh, three large-scale portraits and one commercial billboard supporting his bid for re-election, sponsored by a bank.

All the signs are of an active and exciting election campaign

Cars, shops and houses throughout Yemen are plastered with images of the president, his four rivals and the numerous local election candidates.

Thousands of people are turning out every day to hear the presidential candidates speak at mass rallies in every major city.

At home, people are tuning into extensive media coverage on state-run television and the newspapers are dominated by election issues.

On the surface, this appears to be a vital and popular election campaign in full swing.

Unequal prospects

But such overt displays of participation and support should not be taken at face value, says Hafez Bukari, director of the Yemen Polling Centre.

We've been talking about democracy in Yemen for 15 years, but there's never been an opportunity for change - this time it's different

Ali Saif HassanPolitical Development Forum

"A lot of stickers on cars are not about people's genuine political convictions. They just want to protect themselves and on September 20 they could vote for a different candidate."

And Mr al-Bukari argues that the opposition doesn't stand an equal chance.

"Yemenis don't yet have a full understanding of democracy. Many people simply can't differentiate between the current ruling party and the state."

At 64, after 28 years in power, the president is fighting his second election campaign and faces a serious challenger for the first time.

In 1999, in the first direct presidential election in the Arabian Peninsula, Mr Saleh stood against a candidate from his own party and was elected with a 96% share of the vote.

True challenge

The current challenger, Faisal Bin Shamlan, represents an alliance of the five main opposition parties, including the Yemen Congregation for Reform, the largest Islamist party, Islah, and the Yemeni Socialist Party.

Ali Abdullah Saleh has been in power for 28 years

The 72-year-old economist resigned from his post as oil minister in 1995 in protest over corruption.

"We've been talking about democracy in Yemen for 15 years, but there's never been an opportunity for change. This time it's different," says Ali Saif Hassan, director of Yemen's Political Development Forum, an independent think-tank.

"Now we can assess the president's strengths and weaknesses and compare him to a credible candidate."

But Mr Hassan says that most Yemenis will still vote for Mr Saleh because they have never experienced anything different.

"He has held the centre for 16 years as president of Yemen, and 12 years as leader of North Yemen before unification. People think 'better the devil you know'."

Pressure for reform

Journalist Nasser Arrabyee agrees that President Saleh will win "by hook or by crook" but believes that the crucial factor is the margin of victory.

Faisal Bin Shamlan is being seen as a credible challenger

"If Bin Shamlan gets 30% or 40% of the vote, will Saleh come under pressure to make substantial reforms in government during his next seven-year term?" he asks.

A recent survey conducted by the Yemen Polling Centre revealed that poverty, corruption and unemployment were the three top priorities for voters in this election.

Ranking among the 50 least developed countries in the world, with a weak economy and rapid population growth, Yemen certainly faces considerable challenges in the years ahead.

One long-term observer of Yemeni politics who has visited the country on a regular basis during the last 10 years says she is struck by the palpable sense of unrest and outspoken need for reform that is evident in this campaign.

"These election results may not be earth-shattering, but they will set in train profound changes. Yemen can't afford to stand still if its people are to have a decent chance."